The LAC-line snail, discovered by Cooper, et al, 1994, has been used to study the resistant phenotype in the snail Biomphalaria glabrata which is the invertebrate host for Schistosoma mansoni. LAC-line was derived from the high susceptible NMRI snail and in addition to its differences in schistosome compatibility from NMRI, it also exhibits abnormalities in its reproduction. To determine molecular differences between the two snail stocks, the albumen gland was examined because of the role it plays in both snail reproduction and internal defense. Differential screening of a NMR albumen gland cDNA expression library yield several closes with a strong positive reaction toward the LAC-11-like strain when screened with serum produced by injecting soluble protein from either LAC or NMRI albumen glands in mice. One clone that was sequenced, pBGC2 had a 78% similarity to the antioxidant enzyme, thioredoxin peroxidase (TPX). The goal of this present proposal is to examine differences in the expression of TPx in the albumen gland between LAC-line (resistant) and NMRI (susceptible) stocks and determine if this enzyme occurs in other resistant sticks such as BS90 and 10R2. We will continue to test the hypothesis that the phenotypic variations seen distribution of the TPx gene among other snail tissues will be determined. Further, we will investigate molecular differences among the Amebocyte Producing Organ (produces hemocytes and is the major hemopoietic organ in B. glabrata) of susceptible NMR and resistant LAC-line, 10R2 and BS90 snail lines. The ultimate goal of this research is to determine the molecular factors or the gene responsible for the resistant phenotype.